Group data by weeks

Group data by weeks

To group correctly by weeks also between years you need code like this one. Otherwise if you group only by DATEPART, it will aggregate the same week numbers over multiple years.

SELECT

 DATEADD(week, DATEDIFF(week, 0, DateColumn), 0) AS WeekStart

FROM ATable

GROUP BY DATEADD(week, DATEDIFF(week, 0, DateColumn), 0)

To ensure that the start of week is Sunday, you have to 

SET DATEFIRST 7

Details are on

MSDN SET DATEFIRST

https://social.msdn.microsoft.com/Forums/en-US/d37efbb4-e2b4-4047-961c-3175318f7d24/group-data-by-weeks?forum=transactsql